U.S. patent application Ser. No. 07/911,345 filed on Jul. 8, 1992 now U.S. Pat. No. 5,271,444 invented by the same inventor of this application, discloses a nest tire structure having a solid inner tire secured in an outer tire, whereby upon a breaking or leaking of the outer tire, the solid inner tire will be received by an inner-tire seat formed on a steel rim secured with the outer tire to prevent a sudden collapse of a car due to a run-flat tire.
Upon puncture of a broken tire, the tire will become flat to couple the solid inner tire 30 with the inner-tire seat 201, and heat will be produced due to friction between the solid inner tire 30 and the seat 201 of the steel rim 20 under rotation of the run-flat tire of a car wheel, to possibly cause fire accident or even injury to the car driver or passengers.